In this study, a distribution of chain-length of amylopectin and gelatinization properties of rice starch prepared from six varieties, namely Koshihikari, Sasanishiki, Akitakomachi, Varieties A (high amylose rice), Varieties B (high protein rice) and Nipponbare, were investigated. The following results were obtained. The distribution of chain-length of amylopectin, expressed as a value of Fr.III/ Fr.II, were 3.52 for Koshihikari, 3.78 for Sasanishiki, 3.72 for Akitakomachi, 4.98 for high-amylose rice, 4.13 for high-protein rice and 3.38 for Nipponbare. The long-chain content of Koshihikari was especially high as 12.5 mol% whose average chain-length was 50 to 60 compared with five other varieties. Although a chain length of 10 to 20 was dominant in the short-chain of other varieties, 37.5 mol% of that of Koshihikari was less than 10. The average chain-length of the sum of Fr.II and Fr.III was 21 to 23, and no difference was observed between varieties. However, the average chain length of Fr.III was 10.6 in high-amylose rice, showing a tendency of being shorter than those of the other five varieties. The proportions of B₃ chain, B₂ chain, and A+B₁ chain of amylopectin were 4.2 to 12.5, 12.5 to 20.8, and 68 to 79.2 mol% in nonglutinous rice starch, so nonglutinous rice starch had a larger mol% for the long-chain fraction of amylopectin and a small mol% for the short-chain fraction of amylopectin compared with 1.1, 8.0 and 90.0 mol% of the corresponding fractions in glutinous rice starch. The complex elastic modulus (G*) of the dynamic viscoelasticity of rice starch suspensions at 95°C showed the following order, from the higher to the lower, Koshihikari, Nipponbare, Akitakomachi, Sasanishiki, High protein, High amylose rice. The negative correlation of r=-0.871 was observed between the Fr.III/Fr.II value and the complex elastic modulus (G*) of the dynamic viscoelasticity. In addition, a negative correlation of r=-0.963 was observed with respect to the transition calory of DSC.

View full abstract

Dynamic viscoelasticities of cooked rice grains were measured using an instrument for evaluating dynamic viscoelasticity of irregularly shaped and small samples in the doubleside shear mode. Viscoelastic parameters, modulus G', dynamic loss G'' and loss tangent tanδ were obtained for five varieties of rice which had different amylose (17.5-30.0%) and protein (6.5-11.6%) contents. Treatments performed on these samples, included conductive heating by means of an electric rice cooker, steaming and microwave heating. For the coefficient of varience, these tanδ values were less than 5%, in contrast to both G' and G'' which were more than 10%. These tanδ values were not influenced very much by water content or polishing rate of grains, while they were substantially affected by the treatments and aging at room temperature. Each variety treated by conductive heating could be classified with respect to tanδ values which were between 0.175 and 0.335. In the case of equal value of tanδ, those varieties could be classified by their dynamic modulus. On the other hand, it was found that tanδ related amylose content and the breakdown viscosity by amylography from chemical and rheological analyses. As a result, the use of tanδ as the index of the breakdown properties of the starch granules upon heating was suggested.

View full abstract

The experimental results of appearance of 2, 6-dichlorophenol in carrot treated with sodium hypochlorite were as follows: (1) Mass chromatographic method was employed to detect a trace amount of 2, 6-dichlorophenol reported as the compound responsible for off-flavor. (2) 2, 6-dichlorophenol was formed in carrot treated with sodium hypochlorite without any contamination of phenol. (3) 2, 6-dichlorophenol was formed by heating carrot immersed in sodium hypochlorite of more than 100ppm (available chlorine) for 15min. (4) 2, 6-dichlorophenol was formed in heated carrot treated sodium hypochlorite, more than F₀ = 1.0 min (at 121.1°C, Z = 10°C). In conclusion, 2, 6-dichlorophenol participated particularly in off-flavor production from carrot treated with sodium hypochlorite, especially in the case of sterilization process using sodium hypochlorite.

View full abstract

Effects of the addition of whey protein isolate (WPI) and soy protein isolate (SPI) on the texturization of rennet casein were investigated. Three types of textured casein products which were made from rennet casein alone (control), a blend with WPI, and a blend with SPI, respectively, were prepared. WPI and SPI were blended with rennet casein at. a level of 5% on a dry basis. Fibrous structure of the textured product which was made from rennet casein alone tended to deteriorate during storage. Fibrous structure of the product blended with WPI was satisfactory, while that with SPI was even inferior to that of rennet casein alone. Surface hydrophobicity of each textured product was determined by using 1-anilino8-naphthalene-sulfonate (ANS) and hydrophobic gel chromatography. Fibrousness of textured products were found to be closely related as inversely proportional to hydrophobicity. The product blended with WPI, showing the lowest hydrophobicity, revealed the highest fibrousness among the three types, while the product blended with SPI, with the highest hydrophobicity, resulted in the poorest fibrousness. It was considered that an addition of WPI to rennet casein possibly prevented mutual adhesion of fibrous structure in the resultant product due to a decrease of hydrophobicity, whereas an addition of SPI promoted the adhesion due to an increase of hydrophobicity.

View full abstract

A strain of mold having milk clotting protease was isolated from soil, and identified as Aspergillus ustus. The crude enzyme from wheat bran culture was purified by salting-out and several column chromatographic methods. In the final stage, the enzyme was refined to a unique protein of which milk clotting activity (MCA) was 18.7 fold of the crude enzyme. The molecular weight was estimated to be 86 kDa. MCA increased with a decrease of pH within the pH range 5.0 to 6.75 but proteolytic activity (PA) was optimum at pH 6.0, and both activities were stable in pH 6.3-6.0. Optimum temperature was 63°C for MCA and 50°C for PA. Inactivation by heating was observed at 55°C in both MCA and PA. Ca²⁺ was much effective on MCA, but not on PA. Km value of PA to casein was 0.27%. Some metal ions affected both activities, and inhibition of NEM and SDS were considerable. Decomposition of α_s1-casein was lower, and that of β-casein was higher by the A. ustus enzyme than by chymosin, but no considerable difference in their activities was observed toward k-casein.

View full abstract

The starch was prepared from kiwifruit during post-harvest ripening. (1) Scanning electron microscopies showed a gradual disintegration of tissues and a decomposition of a surface of the starch. (2) Photopastegram of kiwifruit starch showed that the initial temperature of gelatinization dropped by ripening, from 66°C to 64°C after 6 days storage, and to 62°C after 12 days storage. Decrease of transmittance was not observed prior to the drop of initial temperature of the gelatinization. (3) Kiwifruit starch showed B-pattern on X-ray diffractometry and the pattern did not change during ripening. (4) Kiwifruit starch was debranched by isoamylase and fractionated to three fractions (F-1, F-II and F-III) by gel-filtration on Sephadex G-75 .By measuring of λmax, it was suggested that F-I was originated from amylose, and F-II and F-III was originated from amylopectin. Amylose (F-I) content increased during ripening from 8.1% to 13.0% after 6 days storage and 19.1% after 12 days storage. It was estimated that the increase was caused by decomposition of amylopectin. The degree of polymerization of F-II and F-III were in the range of 34-36 and 14-16, respectively, throughout the ripening.

View full abstract

Heat resistance parametric value, D (Decimal reduction time), was investigated to estimate the sterilizing value to inactivate spores of Bacillus coagulans in a food product having a specific combination of pH and water activity (Aw) values. The spores were heated and cultured in a medium containing 0.1% polypeptone, 0.3% yeast extract, 0.2% beef extract, and 0.1% glucose and adjusted to the desired pH and Aw. The minimal growth pH was 4.5 at Aw ca. 1. The minimal growth Aw at pH 7.0 was 0.98 in the medium to which sodium chloride was added as the solute, 0.97 to 0.98 for potassium chloride, 0.94 for sucrose and 0.92 for glycerol.
The apparent D value was determined for sodium chloride at a combination of pH, 4.5 to 7.0, and Aw, 0.98 to 1. Based on the data obtained, a mathematical formula for estimating the D value at an individual co-bination of the two factors was developed.

View full abstract

The effect of the addition of α-lactalbumin and β-lactoglobulin fractionated from whey protein isolate (WPI) on the texturization of rennet casein was investigated. Each whey protein component was added to rennet casein at a level of 5% on a dry basis. Surface hydrophobicity of each textured casein product was determined by using 1-anilino-8-naphthalene-sulfonate (ANS) and hydrophobic gel chromatography. An addition of β-lactoglobulin was found to be effective on decreasing the hydrophobicity of the resultant textured product, whereas α-lactalbumin was not. A decrease of the hydrophobicity, which was shown when β-lactoglobulin was added, was possibly associated with the formation of β-lactoglobulin-casein complex during cooking. The fibrousness of the product blended with β-lactoglobulin was superior to that containing α-lactalbumin. It was indicated that β-lactoglobulin contained in WPI played a major role in improving the fibrousness of the resultant textured product.

View full abstract

Persimmon vinegar production from brewed persimmon (cv. Fuyu) was investigated using immobilized Acetobacter aceti (IFO 3283) cells by a horizontal rotary drum reactor. Fermentation was carried out at 30°C in rotating three vessels containing silicon rubber at 10rpm, and was continued for 40 days. Contents of citric acid, succinic acid and malic acid little decreased at the early stage of fermentation. The free amino acid content decreased during the fermentation.

View full abstract

Suitabilities of 13 kinds of newly bred rice varieties and lines as materials for rice crackers were investigated by the ordinary manufacturing test methods in a laboratory scale. Expansion rate of rice crackers showed a highly negative correlation with a ratio of final viscosity to peak viscosity on amylogram. Therefore, it would be possible that expansion rate of rice crackers estimated by this ratio. Low amylose rice was found to be suitable for soft-type rice crackers because it expanded well. On the contrary, high amylose rice was found to be unsuitable for soft-type rice crackers because it did not expand well. However, Hosiyutaka was markedly improved for the hard-type rice crackers by adjustment of the gelatinizing conditions. The size of grain did not affect to the quality of rice crackers. However, rice with characteristic granular size should be milled carefully because their bran layers are thick and easily break during milling. The flavour of aromatic rice was favourable for rice crackers. However, in case of blending 30% of aromatic rice and 70% of ordinary rice, the flavour did not remain in rice crackers. Rice which had suitabilities for soft-type rice crackers could be used as a material for hard-type rice crackers by proper processing conditions. On the contrary, rice which had suitabilities for hard-type crackers could not always use as a material for soft-type crackers. On the conclusion, there are two kinds of rice for crackers in view of that soft-type rice crackers need high expansion, and hard-type crackers do not need.

View full abstract

Plasmin and plasminogen activities and casein degradation during ripening of Swiss-type cheese made from raw milk were studied. The average contents of plasmin of raw milk and green cheese were 18 nmol pNA/ml and 436 nmol pNA/g, respectively. The level of plasmin activity in cheese decreased gradually over a period from 1 to 20 days during ripening and then maintained the same level until the end of ripening (90 days). Thus there was a significant decrease (P<0.05) in plasmin activity between day 1 and 20, but there were no significant differences (P<0.05) in plasmin activity among 20, 40, 60 and 90 day samples of the cheese. The range in plasminogen activity for green cheese was from 708 to 880 nmol pNA/g, with an average of 819 nmol pNA/g. The course of the curve representing change of plasminogen activity during cheese ripening showed similar results with that of plasmin activity. Electrophoretograms of the proteins in the cheese indicated that as the ripening age of the cheese increased, major caseins were broken down, i. e., αs1-casein intoas1-I-casein and also β-casein into γ1-, γ2- and γ3-caseins. The αs1-casein in ripening of the cheese was degraded faster than the β-casein so that in 90 days old cheese only 22% and 46%respectively of these proteins remained intact.

View full abstract

[in Japanese]

View full abstract